When we left our overachiever 4.8L-powered Chevelle last month, we had managed to nitrous shock our 3,650-pound Chevelle into some amazing 12-flat quarter-mile times. The Chevelle ran this number despite a hideous 1.95 60-foot time, because the only way to not spin the tires was to launch the car soft and wait until the 60-foot mark to smack the nitrous. This was a ready-made situation for the Lingenfelter Performance Engineering (LPE) nitrous control computer, which promised to launch the Chevelle much more efficiently.

To recap last month’s adventure, we started with a 100,000-mile 4.8L truck engine we swapped into our Orange Peel ’66 Chevelle. All we added was a mild 219 degrees at 0.050 Comp hydraulic roller cam, new springs, an Edelbrock dual-plane intake, a vacuum secondary 750-cfm Holley carburetor, and an MSD ignition box. We swapped the tiny LS motor in the car with help from a Champ oil pan, and because the motor was so undersized, we didn’t bother with headers, opting instead for a budget set of Hooker cast-iron manifolds. On engine power alone, the 4.8L revealed why few car crafters would think to mess with this engine. Our best normally aspirated pass was an eighth-mile 8.47 at 85-mph run that is equivalent to 13.29 at 105 mph in the quarter. We thought that a 150hp shot of nitrous would get us in the mid-12s and that would be cool. Surprisingly, even with our sundial-slow 60-foot, we were knockin’ on the 11-second door. That 4.8 was just a short skirt teasing us—we had to go quicker.

The key to entering the 11s would be the LPE nitrous control computer NCC-002*. The NCC unit is designed to pulse-width modulate the nitrous and fuel solenoids, and that allows us to use a single stage of nitrous yet launch with a softer hit. Our first full 150hp shot on the starting line created nothing but tire spin. Rather than work on the suspension, we anticipated quicker results by modulating the nitrous. The computer was originally designed to be used with EFI cars, but it’s just as happy with a carburetor. If you’re not afraid of laptops, you can modify the configuration digitally. Or it’s just as easy to change parameters with buttons and the direct readout screen.

2/10The LPE nitrous controller looks intimidating with its 26 separate connections, but we only used 12. Any parameter can be changed quickly by punching buttons—or you can reconfigure with a laptop. After mounting our box behind the glovebox, we think it would have been more convenient to mount it fingertip accessible on the dash.

The NCC Nitrous 1 position offered a simple setup that allowed us to set the initial percentage of nitrous, followed by a gradual increase in volume. The NCC box does this by pulse-width modulation of the solenoid. This works just like a duty cycle. We initially configured the box so the solenoids begin at a 20 percent duty cycle, gradually ramping up to 100 percent duty cycle after 2 seconds. A separate NCC feature allows you to delay the nitrous solenoid (we chose 0.10-second after the fuel solenoid) so the fuel can get a head start into the manifold and prevent a lean air/fuel-ratio spike. This is accomplished because the NCC controls the nitrous and fuel solenoids with separate relays. We also wired the NCC to send a 12-volt signal to the MSD to retard the timing at the exact moment the nitrous engages.

The NCC box offers several other control functions that can be very useful. An optional fuel-pressure sensor (0–15 psi in our case, 0–150 psi for EFI) allows the NCC to monitor fuel pressure and act as a safety shut-off should the pressure drop below a configurable minimum pressure. There’s also an optional nitrous pressure sensor that can be set to monitor bottle pressure and control an electric bottle heater. We also took advantage of a simple function that allows you to command a given percent of nitrous engagement when the throttle is reapplied should you have to lift. We chose to reapply the nitrous at 50 percent rather than 100 percent, as would be the case with a simple on/off switch.

Track Tested

Before we hit Irwindale again, we had a chance to run the Chevelle with the nitrous tune-up by driving up into the high desert north of Los Angeles to Willow Springs Raceway, where they were holding a Saturday night 1,000-foot drags. The most important thing we learned was that we could hit the tires harder at 30 percent on the starting line and be more aggressive with the nitrous earlier in the run. While we did that, our bottle heater failed, so our nitrous pressure was low. The worst part, however, was that we were at 3,500 feet of altitude, which means thin air. The best the Chevelle ran that night was a 1,000-foot time of 10.52 at 105.9 mph. Our best estimate is that this equates to a 12.77 quarter-mile time—way short of our 11.90 goal. We repaired the bottle-heater wiring, added a fresh NOS 10-pound bottle, and waited for Irwindale’s Test ’n’ Tune night.

3/10LPE recommends that when modulating nitrous solenoids to use a Hella electronic relay (foreground). They are expensive but can modulate at as much as 1,000 times per second (Hz). We used two Hellas, one for nitrous and one for the fuel solenoid.

Irwindale is usually very crowded, so we chose to jump right into our nitrous test. We also brought along a newer pair of Mickey Thompson E.T. Street tires when we discovered our original tires were 11 years old. Our new NCC tune consisted of hitting the nitrous at 2,800 rpm with 30 percent and ramping quickly to 100 percent in 1.8 seconds. This produced an odd situation when the car left really soft with a slow 1.945 60-foot and only ran a 7.91 at 93.38. This was much slower than we expected, and it was clear the nitrous was not engaging right on the starting line. After much head-scratching, we realized that new carpet underneath the throttle pedal was preventing the last 10 percent of throttle opening, so the linkage was engaging the nitrous only after the car was well into the run. We adjusted the linkage to lift the pedal off the floor slightly, and we were ready to try again. Now that the nitrous was really hitting, the Chevelle shot off the starting line with a 1.678 60-foot (its best ever) and blasted an incredible 7.26 at 96.03 mph. That equates to a quarter-mile time of 11.40 at 119.08 mph. We were stoked and decided we needed to back this up. Now empowered with our newfound control of the nitrous beast, we bumped the initial hit to 38 percent, achieving 100 percent in 1.7 seconds. All this was in an attempt to improve our 60-foot time. Basically, after 1.7 seconds, the nitrous system works just like any simple nitrous kit, so our best opportunity for a better e.t. was to improve our 60-foot times.

The car launched hard and hooked, but then we could feel the tires spin slightly, and the time clocks recorded a slightly slower 60-foot time of 1.763, which meant our overall time slowed to a 7.420 at 96.44. But this still equated to an 11.64 and improved the trap speed to 119.58. It was clear we needed suspension work now if we were going to go quicker. While we have a relatively small 8.5-inch-wide tire, there are plenty of cars running a lot quicker than our high 11s on these same tires.

5/10From the start of this test, the Chevelle was running these Global West anti-squat brackets that lower the rear mounting point of the lower control arms to move the instant center and improve traction. We are also using the Global West tubular lower control arms with the Del-A-Lum bushings.

While we were thrilled with that first quick pass at Irwindale, there is more e.t. to be gained. On that pass, the bottle pressure was low due to an intermittent bottle heater that only worked when it wanted to—bottle pressure was around 875 psi on the final two passes. Despite that, the Orange Peel has run much quicker than we ever thought possible—11.40s. We have a list of about a dozen things we’d like to try, including headers, a 4.10:1 gear, and a nitrous plate blueprint, among the more popular ideas. The obvious choice is to just hit our little LS with more nitrous, but that’s too easy. We’re not ready to talk about running in the 10s yet, but low 11s certainly seem possible. We still have to be wary of our stock, cast pistons.

6/10We often tuned the LPE NCC just by pressing buttons on the controller, but it can also be adjusted via laptop. The NCC box also has an internal data logger that we’ve just started using. This curve shows the ramp rate of the solenoids.

7/10We also converted all the Chevelle’s braided rubber fuel lines to TechAFX -8 PTFE (PolyTetraFluoroEthylene—we can’t call it Teflon) conductive-core fuel hose because we have had problems with rubber braided steel lines cracking and leaking fuel. This is due to reformulated, alcohol-laced pump gas that is now common. The TechAFX hose PTFE lining is impervious to all fuels, including E85 and methanol. Yes, it’s more expensive and requires specific hose ends.

Chassis Work

While temporary fixes like adding an airbag or a stiffer coil spring on the passenger-side rear would help to prevent the rear axle from lifting the right side due to normal torque reaction, the best solution is a dedicated antiroll bar. This is not the same thing as a rear sway bar. An antiroll bar looks like a sway bar, but rather than connecting to the lower trailing arms, the antiroll bar clamps the bar to the axlehousing and then uses adjustable links that attach directly to the car’s frame. This is exactly how the BMR antiroll bar works, which is what we mounted on the Chevelle. There are also two mounting holes on the bar to adjust the amount of leverage applied to the frame through the bar. A slight amount of preload can also be applied through the endlinks.

8/10Since the potential for higher speeds is inevitable, we decided to dump the stock upper and lower control arms in exchange for a set of Global West drag race specific tubular arms. The uppers are lighter and add more caster, reducing bumpsteer, while the lowers are constructed of chrome-moly tubing. We also added Global West drag race front springs to help the launch.

We were also concerned about safety when we discovered a crack near the ball joint in the passenger-side lower control arm. That was enough to convince us to trash all four original arms in favor of new Global West tubular drag race upper and lower controls arms for the front. Several years ago, we replaced the trailing arms in the rear suspension and added an upper control arm brace, but now it was time for the front suspension. We also added new, tall Global West drag-race front coil springs to improve weight transfer under acceleration. We also need more adjustable shocks for the Chevelle. Unfortunately, our story deadline prevented us from installing these suspension pieces quickly enough to get back to the track, so our test of the Orange Peel’s new suspension will have to wait, but the results appear promising.

9/10The Global West tubular front lower control arms eliminate the front sway-bar mount, so to control body twist we added this BMR rear antiroll bar that clamps to the rear axle. The bar allows tuning with two different front connections, and it’s possible to preload the bar with the end links. A minor amount of preload can counteract body twist.

Nitrous Tuning

These numbers are not Holley’s published tune for the NOS Cheater system. These are what we used with a true 6-psi fuel pressure and 950-psi nitrous pressure, and we found these leaner fuel numbers worked well and made more power. Of course, we also retarded timing by 8 degrees and used cold plugs.

Nitrous HP

Nitrous Jet

Fuel Jet

150 HP

0.063

0.057

180 HP

0.073

0.065

210 HP

0.082

0.076

250 HP

0.093

0.085

10/10Just so you don’t think we’re making this stuff up, here is our time slip for the 7.26 pass. Our car number was 0490 in the left lane.